Some Delta Air Lines flights were set for take-off after being grounded Monday morning following a power outage in Atlanta that affected the company's computer systems.
"Customers heading to the airport should expect delays and cancellations," the US-based company said on its website about an hour after announcing mass global cancellations and delays for Monday.
"Large-scale cancellations are expected today," the company said in an earlier statement. "All flights en route are operating normally."
The company didn't provide an expected time frame for when the flight schedule would entirely return to normal.
"There may also be some lag time in the display of accurate flight status at delta.com, the Fly Delta App and from Delta representatives on the phone and in airport," the company said.
Screens at airports were also incorrectly showing Delta flights as on time.
Passengers at several airports around the US complained early in the morning via Twitter about being stuck on planes at departure gates, while some who had already boarded flights were asked to exit the planes.